Intravascular ultrasound imaging with frequency selective imaging methods and systems

1. A method for generating an intravascular ultrasound image, the method comprising the steps of: emitting acoustic energy from an ultrasound transducer at a first frequency and receiving a backscatter of the acoustic energy at the ultrasound transducer to acquire a plurality of first frequency data vectors representing one or more items in an imaging view at the first frequency, wherein each data vector comprises ultrasound data; emitting acoustic energy from the ultrasound transducer at a second frequency and receiving a backscatter of the acoustic energy at the ultrasound transducer to acquire a plurality of second frequency data vectors representing one or more items in the imaging view at the second frequency, wherein each data vector comprises ultrasound data, and wherein the first frequency is greater than the second frequency; forming, from the plurality of first frequency data vectors, a first set of data vectors comprising ultrasound data at the first frequency; forming, from the plurality of second frequency data vectors, a second set of data vectors comprising ultrasound data at the second frequency; applying a first filter to the first set of data vectors to form a first modified data set, wherein applying the first filter to the first set of data vectors comprises applying a smoothing filter to the first set of data vectors to form the first modified data set, wherein applying the smoothing filter to the first set of data vectors comprises constructing a first pyramid in which a first level of the first pyramid includes an image at a first resolution and a second level of the first pyramid includes the image at a second resolution, the first resolution being a greater resolution than the second resolution, wherein the image included in the first level of the first pyramid is based on the first set of data vectors and the image included in the second level of the first pyramid is based on the image included in the first level of the first pyramid; applying a second filter to the second set of data vectors to form a second modified data set, wherein applying the second filter to the second set of data vectors comprises applying a smoothing filter to the second set of data vectors to form the second modified data set, wherein applying the smoothing filter to the second set of data vectors comprises constructing a second pyramid in which a first level of the second pyramid includes an image at a first resolution and a second level of the second pyramid includes the image at a second resolution, the first resolution being a greater resolution than the second resolution, wherein the image included in the first level of the second pyramid is based on the second set of data vectors and the image included in the second level of the second pyramid is based on the image included in the first level of the second pyramid; determining a frequency response of one or more items in the imaging view based on the first and second modified data sets; and outputting the intravascular ultrasound image on a display based on the frequency response of one or more items in the imaging view.

2. The method of claim 1 , wherein determining the frequency response of one or more items in the imaging view comprises the step of: calculating a difference between the first modified data set and the second modified data set to ascertain whether any items in the imaging view exhibit an increase in response to the acoustic energy at the first frequency compared to the second frequency.

3. The method of claim 2 , wherein determining the frequency response of one or more items in the imaging view further comprises the step of: calculating a difference between the second modified data set and the first modified data set to ascertain whether any items in the imaging view exhibit a decrease in response to the acoustic energy at the first frequency compared to the second frequency.

4. The method of claim 3 , wherein outputting the intravascular ultrasound image on the display comprises the steps of: calculating an output value for first and second colors of a three color output, where the output value is equal to the sum of the first set of data vectors and a product of a difference between the second modified data set and the first modified data and a weighting factor; and using the first set of data vectors as a color value for a third color of the three color output.

5. The method of claim 3 , wherein outputting the intravascular ultrasound image on the display comprises the steps of: calculating an output value for first and second colors of a three color output, where the output value is equal to the sum of 1) the first set of data vectors and 2) a product of a difference between the second modified data set and the first modified data, a weighting factor, and the second set of data vectors; and using the first set of data vectors as a color value for a third color of the three color output.

6. The method of claim 2 , further comprising using a difference between the first modified data set and the second modified data set to determine an interface between two items in the imaging view.

7. The method of claim 6 , wherein the interface is determined to be the interface of a vessel border and blood within the vessel, wherein the location of blood within the vessel is determined based on the blood exhibiting an increase in response to the acoustic energy at the first frequency compared to the second frequency.

8. The method of claim 2 , further comprising using an extent of the increase in response to the acoustic energy at the first frequency compared to the second frequency to differentiate blood and plaque within a vessel, and outputting the intravascular ultrasound image on the display to distinguish the blood and plaque in the image.

9. The method of claim 1 , wherein acoustic energy at the first frequency is emitted and received at a same longitudinal location of the ultrasound transducer within a vessel as acoustic energy at the second frequency.

10. The method of claim 9 , wherein the acquired plurality of first and second frequency data vectors are distributed circumferentially around the same longitudinal location, and wherein adjacent data vectors alternate to comprise ultrasound data at the first frequency and the second frequency.

11. The method of claim 1 , wherein forming the first set of data vectors further comprises including a first number of first frequency data vectors in the first set, wherein forming the second set of data vectors further comprises including a second number of second frequency data vectors in the second set, and wherein the first number and the second number are different.

12. The method of claim 1 , wherein the smoothing filter applied to the first set of data vectors is a Gaussian blur and the first pyramid is a Gaussian pyramid, and wherein the smoothing filter applied to the second set of data vectors is a Gaussian blur and the second pyramid is a Gaussian pyramid.

13. The method of claim 1 , wherein applying the second filter to the second set of data vectors further comprises the step of: applying a sharpening filter to the second set of data vectors after applying the smoothing filter.

14. The method of claim 12 , wherein applying the first filter to the first set of data vectors further comprises applying a sharpening filter after applying the smoothing filter to construct a first Laplacian pyramid based on the first Gaussian pyramid; and applying the second filter to the second set of data vectors further comprises applying a sharpening filter after applying the smoothing filter to construct a second Laplacian pyramid based on the second Gaussian pyramid.

15. The method of claim 14 , wherein outputting the intravascular ultrasound image on the display comprises constructing the intravascular ultrasound image based on a combination of the first and second Laplacian pyramids.

16. A method for generating an intravascular ultrasound image, the method comprising the steps of: emitting acoustic energy from an ultrasound transducer at a first frequency and receiving a backscatter of the acoustic energy at the ultrasound transducer to acquire a plurality of first frequency data vectors representing one or more items in an imaging view at the first frequency, wherein each data vector comprises ultrasound data; emitting acoustic energy from the ultrasound transducer at a second frequency and receiving a backscatter of the acoustic energy at the ultrasound transducer to acquire a plurality of second frequency data vectors representing one or more items in the imaging view at the second frequency, wherein each data vector comprises ultrasound data, wherein acoustic energy at the first frequency is emitted at a different time than acoustic energy at the second frequency, and wherein the first frequency is greater than the second frequency; forming, from the plurality of first frequency data vectors, a first set of data vectors comprising ultrasound data at the first frequency; forming, from the plurality of second frequency data vectors, a second set of data vectors comprising ultrasound data at the second frequency; applying a first filter comprising a smoothing filter to the first set of data vectors to form a first modified data set; applying a second filter comprising a smoothing filter to the second set of data vectors to form a second modified data set; applying a sharpening filter to the second set of data vectors after applying the smoothing filter; determining a frequency response of one or more items in the imaging view based on the first and second modified data sets; and outputting the intravascular ultrasound image on a display based on the frequency response of one or more items in the imaging view.

17. The method of claim 16 , wherein determining the frequency response of one or more items in the imaging view comprises the step of: calculating a difference between the first modified data set and the second modified data set to ascertain whether any items in the imaging view exhibit an increase in response to the acoustic energy at the first frequency compared to the second frequency.

18. The method of claim 16 , wherein the first modified data set includes a lower resolution than the first set of data vectors, and wherein the second modified data set includes a lower resolution than the second set of data vectors.

19. The method of claim 16 , wherein outputting the intravascular ultrasound image on the display comprises: applying an intensity output for a pixel on the display where the intensity output for the pixel is calculated by dividing the second modified data set by the first modified data set to obtain a quotient and multiplying the quotient by the first set of data vectors.

20. A method for generating an intravascular ultrasound image, the method comprising the steps of: emitting acoustic energy from an ultrasound transducer at a first frequency and receiving a backscatter of the acoustic energy at the ultrasound transducer to acquire a plurality of first frequency data vectors representing one or more items in an imaging view at the first frequency, wherein each data vector comprises ultrasound data; emitting acoustic energy from the ultrasound transducer at a second frequency and receiving a backscatter of the acoustic energy at the ultrasound transducer to acquire a plurality of second frequency data vectors representing one or more items in the imaging view at the second frequency, wherein each data vector comprises ultrasound data, wherein acoustic energy at the first frequency is emitted at a different time than acoustic energy at the second frequency, and wherein the first frequency is greater than the second frequency; forming, from the plurality of first frequency data vectors, a first set of data vectors comprising ultrasound data at the first frequency; forming, from the plurality of second frequency data vectors, a second set of data vectors comprising ultrasound data at the second frequency; applying a first filter comprising a smoothing filter to the first set of data vectors to form a first modified data set; applying a second filter comprising a smoothing filter to the second set of data vectors to form a second modified data set; determining a frequency response of one or more items in the imaging view based on the first and second modified data sets; outputting the intravascular ultrasound image on a display based on the frequency response of one or more items in the imaging view; and applying an intensity output for a pixel on the display where the intensity output for the pixel is calculated by dividing the second modified data set by the first modified data set to obtain a quotient and multiplying the quotient by the first set of data vectors.

21. A method for generating an intravascular ultrasound image, the method comprising the steps of: emitting acoustic energy from an ultrasound transducer at a first frequency and receiving a backscatter of the acoustic energy at the ultrasound transducer to acquire a plurality of first frequency data vectors representing one or more items in an imaging view at the first frequency, wherein each data vector comprises ultrasound data; emitting acoustic energy from the ultrasound transducer at a second frequency and receiving a backscatter of the acoustic energy at the ultrasound transducer to acquire a plurality of second frequency data vectors representing one or more items in the imaging view at the second frequency, wherein each data vector comprises ultrasound data, wherein acoustic energy at the first frequency is emitted at a different time than acoustic energy at the second frequency, and wherein the first frequency is greater than the second frequency; forming, from the plurality of first frequency data vectors, a first set of data vectors comprising ultrasound data at the first frequency; forming, from the plurality of second frequency data vectors, a second set of data vectors comprising ultrasound data at the second frequency; applying a first filter comprising a smoothing filter to the first set of data vectors to form a first modified data set; applying a second filter comprising a smoothing filter to the second set of data vectors to form a second modified data set; determining a frequency response of one or more items in the imaging view based on the first and second modified data sets, wherein determining the frequency response of one or more items in the imaging view comprises calculating a difference between the first modified data set and the second modified data set to ascertain whether any items in the imaging view exhibit an increase in response to the acoustic energy at the first frequency compared to the second frequency; and outputting the intravascular ultrasound image on a display based on the frequency response of one or more items in the imaging view, wherein outputting the intravascular ultrasound image on the display comprises applying an intensity output for a pixel on the display where the intensity output for the pixel is calculated by multiplying a difference between the first modified data set and the second modified data set by a weighting factor to obtain a product and subtracting the product from the first set of data vectors.

22. The method of claim 21 , further comprising using the applied intensity output for the pixel on the display as a color value for first and second colors of a three color output, and using the first set of data vectors as a color value for a third color of the three color output.